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1. Nucleation regime map for liquid bound granules........................................................................................ 1

Bibliografía........................................................................................................................................................ 11

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Documento 1 de 1 Nucleation regime map for liquid bound granules Enlace de documentos de ProQuest Texto completo: Headnote Nucleation is the first step in granulation where the powder and liquid first contact. Two types of nucleation inwet granulation processes are proposed. Drop controlled nucleation, where one drop forms one nucleus, occurswhen drops hitting the powder surface do not overlap (low spray flux 'a) and the drop must wet quickly into thebed (short drop penetration time tp). If either criterion is not met, powder mixing characteristics will dominate(mechanical dispersion regime). Granulation experiments were performed with lactose powder, water, PEG200,and Me HPC solution in a 6 L and a 25 L mixer granulator. Size distributions were measured as the droppenetration time and spray flux were varied. At short penetration times, decreasing ' caused the nucleidistribution to become narrower. When drop penetration time was high, the nuclei size distribution was broadindependent of changes in dimensionless spray flux. Nucleation regime maps were plotted for each set ofexperiments in each mixer as a function of the dimensionless distribution width B. The nucleation regime mapdemonstrates the interaction between drop penetration time and spray flux in nucleation. The narrowestdistribution consistently occurred at low spray flux and low penetration time, proving the existence of the dropcontrolled regime. The nucleation regime map provides a rational basis for design and scale-up of nucleationand wetting in wet granulation. Introduction Granulation is the process of agglomerating fine powdery materials using a liquid binder to give larger granules.This can be achieved in a range of different processing equipment including drums, pans, fluid beds, and highshear mixers. It is an important process in a range of industries including agricultural chemicals,pharmaceuticals, mineral processing, food, and detergents. Wet granulation is complex as many processes are occurring simultaneously in the granulator and eachinfluence the granule attributes. Three granulation mechanisms have been defined (Ennis et al., 1997): * Granule nucleation and binder distribution * Granule consolidation and growth * Granule attrition and breakage. Iveson and Luster (1998) and Iveson et al. (2001b) introduced the idea of a general granule growth regime map.After extensive experimentation and observations of granule growth and deformation behavior, they proposedthat granule growth behavior is a function of only two basic parameters: the maximum pore liquid saturation andthe amount of granule deformation during impact. Notably, there exists two regions of growth where nucleationcan completely control the granule properties: the "nucleation" and "induction" regimes. For a feed formulationthat falls into one of these regimes, the granule attributes depend almost entirely on the wetting and nucleationprocesses. Although the growth regime map indicates when nucleation dominates growth, it does not describehow to control nucleation. This suggests that additional regime maps for granulation are required: one for eachof the three controlling mechanisms listed above. In addition, the growth regime map assumes uniform binder dispersion. If the binder is unevenly distributed, theformulation will cross several regimes, as there will be a distribution of granule saturations at any point in time.The more saturated granules will tend to grow more quickly than dry granules, and a rapidly broadening granulesize distribution results. Understanding how to disperse binder evenly using a nucleation regime map will notonly help control the nuclei distribution, but will lead to more controlled growth (and presumably breakage)behavior as well. Current Understanding of Nucleation

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This article focuses on the nucleation zone, also called the "wetting zone"(Schaafsma et al., 1999) or the "spraysurface" or "spray zone" (Schaafsma et al., 2000). The nucleation zone is the area where the liquid binder andpowder surface first come into contact and form the initial loose agglomerates or "nuclei." The size distributionof these initial nuclei critically depends on the processes happening in the nucleation zone, although otherprocesses in the rest of the granulator (referred to as the mixing zone (Becher and Schliinder, 1997)) maysubsequently alter this distribution. Two processes are important in the nucleation zone. Firstly, there is nuclei formation, which is a function ofwetting thermodynamics and kinetics. Secondly, there is binder dispersion, or effective mixing of the powderand binder, which is a function of process variables. Choosing a poor combination of powder and liquid, or usingan inefficient binder dispersion method, will both produce that is difficult to control and reproduce. When liquid is added by spraying, the spray droplets land on the powder surface and penetrate into the poresforming a nucleus granule. In practice, the liquid may not have enough time to form a nucleus due tointerference from the mixing process occurring simultaneously in the granulator. The need to study the nucleiformation kinetics has only recently been identified (Knight et al., 1998a; Tardos et al., 1997) and some workhas begun in this area. Previously, nucleus formation has been assumed to be rapid. This appears to be true forlow viscosity fluids like water, but analysis of the Washburn equation (for example, Ennis and Luster, 1997), andexperimental reports (Ennis et al., 1991; Kristensen and Schaefer 1994; Schaefer and Mathiesen, 1996; Simonsand Fairbrother, 2000) suggest that viscous fluids display much slower nucleation kinetics.

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Acknowledgments This work was supported financially by the University of Queensland, the Dept. of Chemical Engineering, theInternational Fine Particles Research Institute, and by Merck &Co. Inc., West Point, PA. References Literature Cited References Agland, S., and S. M. Iveson, "The Impact of Liquid Drops on Powder Bed Surfaces," CHEMECA 99,Newcastle, Australia, published by IEAust/IChemE (Sept. 25-29, 1999). Akkermans, J. H. M., M. F. Edwards, A. T. J. Groot, C. P. M. Montanus, R. W. J. Van Pomeren, and K. A. R.Yuregir, "Production of Detergent Granulates," World Intellectual Property Organization (WIPO) WO9858046A1,Unilever, NV (1998). References Becher, R. D., and E. U. Schlinder, "Fluidized Bed Granulation: Gas Flow, Particle Motion and Moisture

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Distribution," Chem. Eng. and Processing, 36, 261 (1997). Brenn, G., T. Helpi6, and F. Durst, "A New Apparatus for the Production of Monodisperse Sprays at High FlowRates," Chem. Eng. Sci., 52, 237 (1997). Danjo, K., A. Kamiya, E. Ikeda, H. Sunada, and A. Otsuka, "Influence of Granulating Fluids inHydroxypropylcellulose Binder Solution on Physical Properties of Lactose Granules," Chem. Phar. Bull. 40,2505 (1992). References Denesuk, M., G. L. Smith, B. J. J. Zelinski, N. J. Kreidl, and D. R. Uhlmann, "Capillary Penetration of LiquidDroplets into Porous Materials," J. of Coll. and Interf. Sci., 158, 114 (1993). Diggins, D., L. G. J. Fokkink, and J. Ralston, "The Wetting of Angular Quartz Particles: Capillary Pressure andContact Angles," Coll. and Surf., 44, 299 (1990). Dunstan, D., and L. R. White, "A Capillary Pressure Method for Measurement of Contact Angles in Powdersand Porous Media," J. of Coll. and Interf. Sci., 111, 60 (1986). Ennis, B. J., and J. D. Litster, "Size Reduction and Size Enlargement," Perry's Chemical Engineers 'Handbook,Section 20, D. Green, ed., McGraw-Hill, New York (1997). Ennis, B. J., G. 1. Tardos, and R. Pfeffer, "A Microlevel-Based Characterisation of Granulation Phenomena,"Powder Technol., 65, 257 (1991). Forrest, S., "Granulation in a High Shear Mixer," Honours Thesis, Dept. of Chemical Engineering, University ofQueensland, Brisbane, Australia (1998). Hapgood, K. P., J. D. Luster, S. R. Biggs, and T. Howes, "Drop Penetration into Porous Powder Beds," J. ofColl. and Interf. Sci., 253, 353 (2002). Hapgood, K. P., "Nucleation and Binder Dispersion in Wet Granulation," PhD Thesis, Dept. of ChemicalEngineering, University of Queensland, Brisbane, Australia (2000). Iveson, S. M., S. Holt, and S. Biggs, "Contact Angle Measurement of Iron Ore Powders," Coll. and Surfaces A:Physiochemical and Eng. Aspects, 166, 203 (1999). Iveson, S. M., and J. D. Luster, "Growth Regime Map for LiquidBound Granules," AIChE J., 44, 1510 (1998). Iveson, S. M., J. D. Luster, and B. J. Ennis, "Fundamental Studies of Granule Consolidation: 1. Effects of BinderContent and Binder Viscosity," Powder Technol., 88, 15 (1996). Iveson, S. M., J. D. Litster, and K. P. Hapgood, "Review of Agitated Wet Agglomeration Processes," PowderTechnol., 117, 3 (2001a). References Iveson, S. M., P. A. L. Wauters, S. Forrest, J. D. Luster, and G. M. H. Meesters, "Growth Regime Map forLiquid-Bound Granules: Further Development and Experimental Validation," Powder TechnoL, 117, 83 (2001b). Jakobsen, R., "Granule Growth in a Drum Granulator: a Study of the Effect of Binder Distribution," MastersDiss., Particle Technology Group, Delft University of Technology, Delft, The Netherlands (2000). Knight, P. C., T. Instone, J. M. K. Pearson, and M. J. Hounslow, "An Investigation into the Kinetics of LiquidDistribution and Growth in High Shear Mixer Agglomeration," Powder Technol, 97, 246 (1998a). References Knight, P. C., and J. P. K. Seville, "Effect of Binder Viscosity on Agglomeration Processes," World Congress onParticle Technology 3, Brighton, U.K., IChemE, U.K. (July 6-9, 1998b). Kokubo, H., S. Nakamura, and H. Sunada, "Effect of Several Cellulosic Binders on Particle Size Distribution inFluidised Bed Granulation," Chem. and Phar. Bull., 43, 1402 (1995). Kristensen, H. G., and T. Schaefer, "Agglomeration with Viscous Binders," First Int. Particle Technol. Forum,Denver, CO (1994). Luster, J. D., K. P. Hapgood, J. N. Michaels, S. K. Kamineni, T. Hsu, A. Sims, and M. Roberts, "Liquid Distribution in Wet Granulation. Dimensionless Spray Flux," Powder Technol.,

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114, 32 (2001). Luster, J. D., K. P. Hapgood, J. N. Michaels, S. K. Kamineni, A. Sims, and M. Roberts, "Scale-up of Mixer Granulators for Effective Liquid Distribution," Powder Technol., 124,272 (2002). Liu, L. X., J. D. Litster, S. M. Iveson, and B. J. Ennis, "Coalescence of Deformable Granules in Wet GranulationProcesses," AIChE J., 46, 529 (2000). Mackaplow, M. B., L. A. Rosen, and J. N. Michaels, "Effect of Primary Particle Size on Granule Growth andEndpoint Determination in High-Shear Wet Granulation," Powder Technol., 108, 32 (2000). Middleman, S., Modeling Axisymmetric Flows: Dynamics of Films, Jets, and Drops, Academic Press, San Diego(1995). Mort, P., and G. Tardos, "Scale-up of Agglomeration Processes using Transformations," Kona, 17, 64 (1999). Mort, P. R., "Dimensional Analysis of Agglomeration: Scale-up using Transformations," World Congress onParticle Technology 3, Brighton, U.K. IChemE, U.K. (July 6-9, 1998). Rankell, A. S., M. W. Scott, H. A. Lieberman, F. S. Chow, and J. V. Battista, "Continuous Production of TabletGranulations in Fluidized Bed: II. Operation and Performance of Equipment," J. of Phar. Sciences, 53, 320(1964). Schaafsma, S. H., N. W. F. Kossen, M. T. Mos, L. Blauw, and A. C. Hoffman, "Effects and Control of Humidityand Particle Mixing in Fluid-Bed Granulation," AIChE J., 45, 1202 (1999). Schaafsma, S. H., P. Vonk, and N. W. F. Kossen, "A New Liquid Nozzle for the Fluid Bed AgglomerationProcess," World Congress on Particle Technology 3, Brighton, U.K., IChemE, U.K. (July 6-9, 1998a). Schaafsma, S. H., P. Vonk, and N. W. F. Kossen, "Fluid Bed Agglomeration with a Narrow Droplet SizeDistribution," Int. J. of Pharmaceutics, 193, 175 (2000). Schaafsma, S. H., P. Vonk, P. Segers, and N. W. F. Kossen, "Description of Agglomerate Growth," PowderTechnol., 97, 183 (1998b). Schaefer, T., and C. Mathiesen, "Melt Pelletization in a High Shear Mixer VIII. Effects of Binder Viscosity," Int. J.of Pharmaceutics, 139, 125 (1996). Schaefer, T., and 0. Worts, "Control of Fluidised Bed Granulation I. Effects of Spray Angle, Nozzle Height andStarting Materials on Granule Size and Size Distribution," Archiv for Pharaci og Chemi, 5, 51 (1997a). Schaefer, T., and 0. Warts, "Control of Fluidised Bed Granulation II: Estimation of Droplet Size of AtomisedBinder Solutions," Archiv for Pharaci og Chemi, 5, 178 (1977b). Schaefer, T., and 0. Warts, "Control of Fluidised Bed Granulation: III. Effects of Inlet Air Temperature and LiquidFlow Rate on Granule Size and Size Distribution. Control of Moisture Content in the Drying Phase," Archiv forPharaci og Chemi, 6, 1 (1978a). Schaefer, T., and 0. Worts, "Control of Fluidised Bed Granulation: IV. Effects of Binder Solution and Atomizationon Granule Size and Size Distribution," Archiv for Pharaci og Chemi, 6, 14 (1978b). References Simons, S. J. R., and R. J. Fairbrother, "Direct Observations of Liquid Binder-Particle Interactions: The Role ofWetting Behaviour in Agglomerate Growth," Powder TechnoL, 110, 44 (2000). Tardos, G. I., M. I. Khan, and P. R. Mort, "Critical Parameter and Limiting Conditions in Binder Granulation ofFine Powders," Powder TechnoL, 94, 245 (1997). Vonk, P., C. P. F. Guillaume, G. J. S. Ramaker, H. Vromans, and N. W. F. Kossen, "Growth Mechanisms ofHigh-Shear Pelletisation," Int. J. of Pharmaceutics, 157, 93 (1997). References Waldie, B., D. Wilkinson, and L. Zachra, "Kinetics and Mechanism of Growth in Batch and Continuous FluidisedBed Granulation," Chem. Eng. Sci., 42, 653 (1987). Watano, S., H. Takashima, and K Miyanami, "Scale-up of Agitation Fluidized Bed Granulation: V. Effect ofMoisture Content on Scale-up Characteristics," Chem. and Pharmaceutical Bull., 45, 710 (1997).

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References Manuscript received Oct. 2, 2001, and revision received Sept. 12, 2002. AuthorAffiliation Karen P. Hapgood, James D. Litster, and Rachel Smith Dept. of Chemical Engineering, University of Queensland, Brisbane, Qld., Australia AuthorAffiliation Correspondence concerning this article should be addressed to K Hapgood. Current address of K. P. Hapgood:Merck &Co., Inc.. WP78A-31, PO Box 4, West Point, PA 19486. Título: Nucleation regime map for liquid bound granules Autor: Hapgood, Karen P; Litster, James D; Smith, Rachel Título de publicación: American Institute of Chemical Engineers. AIChE Journal Tomo: 49 Número: 2 Páginas: 350 Número de páginas: 12 Año de publicación: 2003 Fecha de publicación: Feb 2003 Año: 2003 Editorial: American Institute of Chemical Engineers Lugar de publicación: New York País de publicación: United States Materia de publicación: Engineering--Chemical Engineering ISSN: 00011541 CODEN: AICEAC Tipo de fuente: Scholarly Journals Idioma de la publicación: English Tipo de documento: PERIODICAL ID del documento de ProQuest: 199385307 URL del documento: http://search.proquest.com/docview/199385307?accountid=12268 Copyright: Copyright American Institute of Chemical Engineers Feb 2003 Última actualización: 2012-02-22 Base de datos: ProQuest Central

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BibliografíaCitation style: APA 6th - American Psychological Association, 6th Edition

Karen, P. H., James, D. L., & Smith, R. (2003). Nucleation regime map for liquid bound granules. AmericanInstitute of Chemical Engineers.AIChE Journal, 49(2), 350. Retrieved fromhttp://search.proquest.com/docview/199385307?accountid=12268

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